In man, the ultimate goal of genetic studies is to identify individual genes and their action. With respect to the inheritance of quantitative dental traits however, our knowledge is limited to estimates of heritability and genetic variance. Recent methodological advances has made it possible to test genetic hypothesis through family data in order to resolve the mechanism of gene action. This proposal concerns the use of new analytic methods on human quantitative dental data to discriminate the effects of major genes in the presence of polygenic heritability, the effects of environmental factors that are distributed nonrandomly among families, the genetic mechanisms of linkage and pleiotropy, and the heterogeneity of gene action among families. A unique and extensive collection of human dental casts of family members, supplemented by accurate pedigree and genotype data, is available to us on-hand for study. Dental dimensional, morphological and occlusion traits are defined for measurements. The data will be analyzed both as univariate measures and as multivariate entries on the basis of biologically meaningful factors. To accomplish the above objectives we will use path analysis, the mixed model complex segregation analysis, and quantitative linkage analysis.